Superman perhaps should have been paying more attension, but thanks to the fact he wasn't he hadn't see the men sneaking up on him, he hadn't even heard them coming. So he hadn't been able to avoid the fight. It was fast, he'd made the mistake of using heat vision on one of the mens guns causing it to misfire rather than just heat and fall, the bullet sailed through the air before hitting a chemical vile, setting off a train reaction ending in an explosion that rocked the ground around the super hero. And all though only for the briefest moment, supermans' light went out.